The present invention relates to a process for preparing fatty acid or mono- or polyhydroxy fatty acid esters of polyglycerols from intermediate fatty acid or mono- or polyhydroxy fatty acid esters of isopropylidene derivatives of polyglycerols, in which specific process conditions for the preparation of the fatty acid esters of polyglycerol must be followed.
The invention further relates to the use of the fatty acid esters of polyglycerol prepared by such process as nonionic surfactants, and to skin care and/or cosmetic formulations or ointments, paints and wood-protection agents, in which at least one such nonionic surfactant is used as an emulsifier.
It is already known to prepare fatty acid esters, for example tetraesters, of polyglycerols by heating diglycerol for several days with a large excess of fatty acids, e.g., lauric, palmitic, stearic or oleic acid, but such esters are generally obtained in the form of brown solid or oily compounds (see, e.g., C.A., 41, 2392 (1947)). As a result of the long heating, only heavily contaminated products can be obtained in very poor yields. The tetraesters thus prepared cannot be used as surfactants. The attempt has therefore been made to obtain the corresponding compounds from isopropylidenediglycerol and stearyl chloride in chloroform. However, the required amount of work involved is considerable, since after the reaction the mixture solidifies to give a paste, which must be taken up after 36 hours in benzene. After the aqueous solution is separated off and the organic phase is washed with water, excess stearic acid must be removed by extraction with 10% sodium bicarbonate solution, the organic phase must be dried over sodium sulfate, and the solvent must be distilled off. The resulting residue has to be recrystallized two or several times with alcohols. A further disadvantage of this process is that hydrochlorides are formed in molar ratios, which either have to be processed further or represent polluting substances.